By the time she turned 50, Sharon Monaghan had developed a habit of repeating herself. Then came lapses in memory and judgment. At first, she blamed her cancer treatment. One day, she got frighteningly lost on the way to the doctor.

By the time she turned 50, Sharon Monaghan had developed a habit of repeating herself. Then came lapses in memory and judgment. At first, she blamed her cancer treatment. One day, she got frighteningly lost on the way to the doctor.